1. Field of the Invention
The present invention relates to a method and a relay station for aggregating service connection identifiers in IEEE 802.16.
2. Description of the Related Art
IEEE 802.16 is a standard of the high-speed wireless access system which can provide BWA (Broadband Wireless Access) service.
In IEEE 802.16 standardization meeting, MMR (Mobile Multi-hop Relay) technique to extend a coverage area by RS (Relay Station) is studied. In particular, a MAC (Medium Access Control) and a physical layer are established in this meeting. According to the MMR technique, BS (Base Station) not only communicates with SS (Subscriber Station) or MS (Mobile Subscriber Station) within the coverage of the BS, but the BS also communicates with SS or MS outside the coverage of BS through RS within the coverage of the BS.
Basically, the high-speed wireless access system of IEEE 802.16 is a standard of BWA service for SS which is fixed terminal (for example, refer to document 1, IEEE Std 802.16-2004). This establishes two network topologies as follows; PMP (Point-to-Multipoint) and Mesh. The PMP network is constructed in the ratio of one (BS) to majority (SS) as same as a cellular system generally). On the other hand, the Mesh network is constructed by a plurality of SSs using multi-hop technique.
According to the document 1, the relay function to extend the coverage area is not defined at all. Since an analog RS which only amplifies power of receiving signal transmits a desired Burst Profile determined by communication state between the RS-SS, the communication state between the BS-RS is not considered at all.
The coverage area could be extended by using the Mesh topology in IEEE 802.16-2004. However, Mesh is optional in the document 1, and a frame structure of Mesh does not have compatibility with PMP's one. Further, since a frame overhead size of Mesh is greater than that of PMP, this affects throughput. Furthermore, the Mesh supports only TDD (Time Division Duplex).
This system assumes the use of frequency bands more than 2 GHz is assumed. According to the frequency characteristic, the SS tends to be affected by the topography or neighboring buildings. Thus, the receiving status becomes unstable. In this case, according to the PMP network, more BS needs to be set up.
IEEE Std 802.16e-2005 (refer to document 2) is amendment of document 1 and covers MS which is mobile terminal. This standard supports only PMP as network topology. According to these standards, the base station BS gives service connection identifiers (IDs) to all subscriber station (SS or MS) that communicates with the BS.
Further, according to the IEEE 802.16 standardization meeting, a technique of translating from a plurality of CIDs between the RS-MS to one CID between the BS-RS was proposed (for example, refer to document 3).
(document 1) IEEE Std 802.16-2004, “IEEE Standard for Local and metropolitan area networks, Part 16: Air Interface for Broadband Wireless Access Systems”
(document 2) IEEE Std 802.16e/D12, “Draft IEEE Standard for Local and metropolitan area networks, Part 16: Air Interface for and Mobile Broadband Wireless Access Systems, Amendment for Physical and Medium Access Control Layers for Combined and Mobile Operation in Licensed Bands”
(document 3) IEEE C802.16mmr-05/005r2, “A Recommendation on PMP Mode Compatible Frame Structure”, URL:http://ieee802.org/16/sg/mmr/contrib/C80216mmr-05—005r2.pdf.
However, the coverage of the BS in IEEE 802.16 is wide (a cell radius is 10 km at the maximum). Therefore, there is extremely much number of MSs in communication with one BS. When the BS communicates with a plurality of MSs through the RS, the number of MSs in communication with the BS becomes enormous. The BS must give service connection ID to all MSs. Thus, the number of service connection IDs managed by BS becomes enormous. That is to say, when the number of mobile subscriber stations increases, an overhead managing service connection ID increases too.